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Sunday, January 18, 2015

Fuel Tank Corrosion - Again

Fuel tank corrosion is a repeat topic on the Yahoo Leopard List. Some people have converted to plastic tanks. Others have stayed with aluminum. There isn't a great answer because both have had problems.

In our post Its Not Over Til Its Over - Port Engine Fuel Tank, we described what we thought was the last of the fuel tank problems. Well, we returned to Annapolis this summer (2014) and found another leak in the port fuel tank. We removed the starboard tank and check it. In both cases, we found salt under the tanks. The port tank had a leak along one of the seams and on the bottom of the sump that's built into the tank. We had cleaned up the water around the port tank before. If we can eliminate the salt water intrusion, we will eliminate the source of corrosion.

It took us two trips to the welder to get the port tank fixed. They had tested it after welding by putting about 6-10 lb of pressure in it and looking for the reading to change. But the weld was leaking. They also couldn't find it by spraying it with diluted dishwashing liquid. However, if it was checked with industrial leak detector, which makes industrial-strength bubbles, the leak was seen. Neither of us was happy about the second trip. We had suspected the original weld because it wasn't shiny all the way around. But they said it was good. We'll know better in the future when we see work that we don't trust and do something to double check it.

Water Stains at Hot Water Bulkhead Feed-Thru

We found a lot of orange staining around the engine cooling water loop that goes to the hot water heater where it comes through the bulkhead. Sure enough, the balsa core was wet when we removed the feed-thru fitting. We cleaned out the rotten balsa, filled with thickened epoxy, and bedded the fitting with butyl tape.

We also added drain holes to the low spots on the shelf that holds the fuel tank and the hot water tank. All holes were sealed with thickened epoxy. We'll be checking periodically to see if salt water is finding its way under the tanks.